Electron discharge device of the velocity modulation type



.HHH ....U..|.., H@ .w....

l IN VEN TOR.

6ta/esi 6'. .S'z//m/ BY @a/,way

Arme/yay A Dec. 19, 195o Patented Dec. 19, 1950 UNITED STATES PATENT OFFICE ELECTRON DISCHARGE DEVICE OF THE vVELOCITY MODULATION TYPE George C.' S'ziklai', Princeton, N. J., assignor to Radio Corporation ofAmerica, a corporation of Delaware My invention relates to electron vdischarge devices and associated circuits and particularly to such devices and circuits useful at ultra high frequencies and employing the principles of velocity modulation and inductive output.

In certain types of tubes referred to as velocity modulated inductive output tubes, a beam of electrons is directed along a space path toward a collector. Positioned along the path of the electrons is a means for producing a high frequency electric field to which the electrons are subjected, as a result of which the velocities of the electrons in the stream are varied. The elec- "trons are then permitted to drift along the path vso that slow electrons are overtaken by fast electrons to form groups of the electrons. At the point of grouping, electrons are subjected to a second high frequency electric eld to which they deliver energy and are then collected by the collector. Normally the devices for producing the vfields are cavity resonators which confine the fields and which are apertured to permitl the electrons to pass through the resonators.

In this type of device the random initial velocities of the electrons released from the electron source, usually an indirectly heated cathode,

may drasticallyaiect the eiciency and output of. the system, particularly Wherethe applied voltage in the first ield is of the same order or smaller than the potentials corresponding to the variations in the initial velocities of the electrons before they reach the first high frequency eld. As a result the electrons are not grouped in a desirable manner along the drift space and the groups of electrons do not enter the second high frequency eld in such fashion as to deliver maximum energy to this field. In effect the launching of the electrons taking place purely due to the random initial velocities masks to some degree the bunching effected by the first resonator or accelerating electrode, or again under these conditions the second high frequency field or second cavity resonator is in the right position only for electrons of certain initial velocityrange and therefore only a fraction of the electrons contribute to the output of the device.

Attempts have been made to neutralize or eliminate the electrons which are not in proper phase and whichdo not contribute to the output of the device. However this does not contribute to the efficiency of the device. Under these conditions the alternating voltage output compared to the D.C. input is no better than in conventional` velocity modulated devices althoughan is substantially reduced, thereby improving the` eiciencyand sensitivity of the device.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims, but the invention itself will best be understood by reference to the following description taken in connection with the accompanying drawing in which the iigure is a longitudinal section of one form of electron discharge device of the amplier type and associated circuit made according to my invention.

An evacuated envelope I il is provided at one end with an indirectly heated cathode and gun structure II for supplying a beam of electrons and at the other end with a collector 20. Positioned adjacent the cathode are a pair of preferably curved electrodes in the form of plates I2 and I3 between which the electrons are directed. A constant dierence of potential as indicated is applied between the electrodes so that electrons directed between these electrodes are subjected to a transverse electrostatic eld. As a result of the action of the electrostatic field the electrons are made to travel substantially circular curved paths, such that the slower electrons are deected to the greatest extent and vice versa. In some cases a constant magnetic field normal to the electron path (in the drawing normal to the plane of the drawing) may be used instead of the deflecting plates. This magnetic field could be established, for example, by the magnet I3. The length of the plates is several times the distance therebetween, whereby the electron stream will be deflected through a substantial angle. This angle is shown in the drawing as being about Positioned transversely in the path of the electron stream are a pair of spaced grid mem-- I6 which may be excited by any suitable means. The grids are so positioned that the fast and slow electrons leaving the cathode at any one instant arrive at the surface of the grid I4 at substantially the same instant, the potential of the resonator I6 and grid I4 relative to the potentials of the deflecting plates I2 and I3 caus'-= ing the electrons to continue to travel curved paths in the space between the plates I2 and I3 and the grid I4. The electrons are velocityv modulated in passing between. the grids I4 and I5 by the field set up in the resonator IB, in a manner now well known so that electrons leaving the surface of the second grid I5 have superimposed thereon the acceleration or deceleration caused by the field within the resonator, the acceleration or deceleration depending upon the instantaneous potentials of the grids at the entry of the electron into this space. The electrons' then proceed along a drift path parallel to the longitudinal axis of the straight portion of thetube, wherein the slow and fast electrons become grouped at the frequency of the field within the resonator I5. inasmuch as the faster electrons c'over a greater dist/ance than the slower elec"- trons, the grouping along' a transverse section will occur along a plane inclined at an ang-le to the path of the electrons. In order to utilize the effective grouping a second resonator I9 provided with the grids II and I8 is mounted trans versely and at such an angle to thev path of the electrons that all electrons of each group enter the space between the' grids I1 and Iii4 at substantially the same instant of time; thus fully utilizing all electrons regardless of initial velocity at the cathode IIJ. They electrons after delivering energy to the resonator I9 in a manner now wellV understood, are collected by collector 2l). The spacing between. the resonators I6 and I9 is such that the electrons attain theirv maximum grouping when they enter the reso'- natorv I9 so as to deliver maximum energy to the electric field in this resonator.` The, spacev between the grids I5 and ITI could be, if desired, shielded from outside iniiuences by ar conducting sleeve not shown and electrically connected tot one or both of the resonators. The various required voltages are supplied by meansy of the voltage source 2 I. The output may be coupled to resonator I9 by the coaxial line. and loopl 22..

It will be apparent from this description; thattheoretically all of the electrons: are made. available for supplying energy to the output and the effect of initial random velocities is. substantially neutralized. ThusA the efiiciency of the device ismuch improved as well as the sensitivity.

While I have indicated the preferred embodiments of my invention of which I, am now` awarel and have also indicated only one specific application for which my invention may be,v employed, it will be apparent that my invention` is by no means limited to the exact forms illustrated, or the use indicated, but that many variations may be made in the particular structure used and the purpose'for which it is employed without departing from the scope of my invention asset forth in the appended` claims.

What I claim asnew is:

l. An electron discharge device comprising. means for supplying a stream of electrons: having random initial velocities along an. electron beam path, means adjacent the electron supplyingA means for deliecting said electrons inversely to the random initial velocity of the. electrons,r means for defining a. high. frequency field: inthe path of said electrons and extending transversely to the beam path at a point past the deflecting means, said field causing velocity modulation of said electrons whereby the electrons become grouped, and means for defining a second high frequency field in the path of said electrons and. inclined at an angle to the electron path so that all the electrons of eachgroup arrive at said second high frequency field at substantially the same instant of time.

2'. An electron discharge device comprising means'vfor supplying a stream of electrons having random initial velocities along an electron beam path,` means' adjacent the electron supplying meansV for deflecting said electrons inversely to the random initial velocity of the electrons, cavity resonatormeans for defining a high frequency field in the path of said electrons and extending transversely to the beam path and positioned at a point past the deflecting means, said eld causing velocity modulation of said electrons whereby the electrons become grouped, and a second cavity resonator means for defining a second high frequency field in the path of said electrons and inclined at an angle to said first resonator` means so that all electrons ofl each group arriveV atl said second high frequency eld at substantiallyv the sameV instant of time.

3. An electron discharge device comprising cathode. meansv for supplying a stream of electrons: having random initial velocities along an electron beam path, means adjacent thev electron` supplying means for deflectingsaid electronsl inversely to. the random initial velocity of the. electrons,y a finalelectrode toward which said electrons are. directed, a first cavity resonator meansfor defining ak high frequency field in the pathY ofY saidrelectronsV and along a plane transverse to the beam path at a point past the deflecting means', whereby electrons. with diierent random velocities and. leaving the cathode means at any instant arrive at said. fieldl together, said field imposing a. velocity modulation component on said electrons. whereby the electrons become grouped, and" a second cavity resonator` means for dening a second high. frequency field and positioned between said first cavity resonator means and said angle tov the electron4 path wherebyV the electrons of each group all pass through said second high frequency field at substantially theV Same instant of time.

4, AnA electron discharge device comprising meansf for supplying a; stream of electrons of random initial velocities along an electron beam path, means along said beam. path for deflecting saidelectrons inversely tol their random. initial velocities, and meansdisposed inthe path of said electrons at al point past said defiecting means and cooperating with said deflecting means for causing said electrons to travel along curved paths after said deflection, said last means including meansV forv defining a first high frequency field through which' said electrons' are directed, said' last means being positioned transversely of the beam path, whereby al1 electrons initially leaving said electron supplyingV means at any instant reach said field together, said field dening. means velocity modulating the electrons passing therethrough whereby velocity variations;- are superimposedv on the initial random velocities ofsaid; electrons, said electrons becominggrouped after passage through said field, and

meansl spaced alongv the electron path for dei-- final electrode, said second. cavity resonator means being inclined at an.

iining a second high f-requency field, said last means being Ainclined at an angle to the lelectrc'an path whereby the fast and slow electrons. of each 4,means along said beam pathfor deflecting said electrons inversely to their random initial velocities, and 'means disposed in the path of said electrons at a point past said deflecting means and cooperating with said deflecting means for causing said electronsto travel along curved paths after said deflection, said last means including means for defining a rst high frequency field through which said electrons are directed, said means being positioned transversely of the beam path, whereby all electrons initially leaving said electron supplying means at any instant reach said field together, said field defining means velocity modulating the electrons passingtherethrough whereby velocity variations are superimposed'on the initial random velocities of4 said electrons,

said electrons becoming grouped after passage through said field, and means spaced along the electron path for deining a second high frequency field, said last means lying along a plane inclined at an angle to the electron path whereby the fast and slow electrons of each group' pass through said second field at substantially the same time, said eld defining means including resonators through which the beam path extends and having grids defining said elds.

6. An electron discharge device comprising an elongated envelope curved at one end, means in the curved end of said envelope for supplying a stream of electrons of random initial velocities along a space path through said envelope, an electrode at the other end of said envelope, means along said space path for deflecting said electrons inversely to their random initial velocities, and a first resonator disposed in the path of said electrons at a point past said deilecting means and cooperating with said deiiecting means for causing said electrons to travel along curved paths, the faster electrons travelling paths of greater radii, said resonator including means for defining a high frequency field through which said electrons are directed, said resonator being positioned transversely of the beam path, whereby all electrons initially leaving said electron supplying means at any instant reach said eld together, said resonator velocity modulating the electrons passing therethrough whereby velocity variations are superimposed on the random initial velocities of said electrons, said electrons becoming grouped after passage through said iield, and a second resonator spaced along the electron path for defining a second high frequency eld, said second resonator lying along a plane inclined at an angle to the electron path whereby the fast and slow electrons of each group pass through said second field at substantially the same time.

7. An electron discharge device comprising means for supplying a stream of electrons having random initial velocities along an electron beam path, means adjacent said electron supplying means for deecting said electrons inversely to the random initial velocities of the electrons and causing said electrons to travel along curved paths wherein the faster electrons are deflected to a smaller extent and travel longer paths in a given time than the slower electrons, and cavity .resonator means for'dening a high frequency stant of time.

8. AAn electron discharge. device ,accordingto claim 7, further including ar second cavity reso? nator means for dening a second high frequency Heldin the path `of said electrons, saidv second cavity resonator means being located beyond and inclined at an angle to said r'st resonator means so that all electrons of each group arrive at said second high frequency field at substantially the same instant of time.

9. An electron discharge device comprising means for supplying a stream of electrons having random initial velocities along an electron beam path, means adjacent said electron supplying means for deflecting said electrons inversely to the random initial velocities of the electrons and causingv said electrons to vtravel along curved paths wherein the faster electrons are deflected to a smaller extent and travel longer paths in a given time than the slower electrons, and means for deiining a high frequency field in the path of said electrons, said last-named means being disposed in a plane transverse to the beam path at a point past said deflecting means and so oriented that all electrons leaving the electron supplying means at the same instant of time arrive at said iield dening means at substantially the same instant of time.

10. An electron discharge device according to claim 9, further including means for defining a second high frequency held in the path of said electrons, said last-named means being located beyond and inclined at an angle to said rst iield defining means so that all electrons of each group arrive at said second high frequency eld at substantially the same instant of time.

11. An electron discharge device comprising cathode means for supplying a stream of electrons having random initial velocities along an electron beam path, means for deflecting said electrons inversely to the random initial velocities of the electrons and causing said electrons to travel along curved paths wherein the faster electrons are deiiected to a smaller extent and travel longer paths in a given time than the slower electrons, said deflecting means comprising a pair of spaced curved plates disposed adjacent said cathode means and on opposite sides of the beam path and means connected to said plates for applying constant deflecting potentials thereto, said curved plates having a length several times the distance between the plates whereby the electrons will be deiiected through a substantial angle, and means for dening a high frequency field in the path of said electrons, said last-named means being disposed in a plane transverse to said path at a point past said plates and so oriented that all electrons leaving the electron supplying means at the same instant of time arrive at said eld defining means at substantially the same instant of time.

12. An electron discharge device comprising cathode means for supplying a stream of electrons having random initial velocities along an electron beam path, means for deflecting said electrons inversely to the random initial velocities of the electrons along curved paths wherein ithe :faster :electrons :are `:deflected --to 'a .smaller extent .and 'tnayel longer paths fin a given itime than 'fthe slower electrons, .said idelecting :means comprising .means adjacent "said :cathode means `for eproducing a constantmagnetic ield transt 'verse ato .the .beam path, .and means im* -tdening a .highfrequencytfieldin `the path 'of said electrons, said last-named means being :disposed @in a plane transverse to the beam path at a point past :said .plates :and v:so :oriented that all el'eetrons leaving the electron `'supplying Ameans Aat '-the 'same instant :of time v'arrive at 'said el'd ade- .fining ,means at .substantially the same .instant .of tima A`3.3. `electron discharge device 4comprising Jne'ans :for :supplying a `stream -o electrons having random initial velocities .along an eleetron .beam path, means adjacent Ysaid .electron supplying means :for subjecting .said electrons ito transverse ndeiieeting :forces of lconstant :intensity `for '.a .sub- :stantal distance to eausesaid electrons to travel along substantially .circulai curved paths, .said 'forces Ideflecfting said electrons inversely 'to 4.the :fandom velocities thereof whereby .the 'faster electrons :are deflected to a .smaller :extent .and 5 'rbi-aval longer paths in a :given time than the' `slower leleeimons, land rmeans for defining 1a .high

,frequency eld -in V,the path` of :said electrons, said last-named zmeans .being .disposed in a :plane transverse to said path at a fpoint past .said .de-

iecting means :and so A:oriented vthat r all electrons lleaving,r the electron supplying "means .at .the same .instant lof .time arrive :at .saidmeans 'for dening 1.a :high .frequency '.eld at substantially the same instant-:of time,

GEORGE l-C. lSZIKLAI :REFERENCES CITED The -following :references are fof record lfin the lfe of fthis 4:patent:

UNITED .STATES PATENTS Number :Name .Date

2,272,165 Vaian v'et' al. .Feb. f 3, y1942 275,480 Varian etal.. Mar. 10,1942 32,289.;319 Strobel,... July 7, 1942 2289.370 Fremlin July n.14:1942 .2,407,707 Kilgore Sept. v17, :1946 :2;409119 .Anderson zoet. 15, 1946 

